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| G C 15S 
I.T62 

pOpy J 




UNITED STATES 
COAST AND GEODETIC SUEVEY 

T. C. MENDENHALL 

SUPERINTENDENT 



WEIGHTS AND MEASURES 



ON THE REDUCTION 



HYDROMETER OBSERVATIONS 

OF 

SALT WATER DENSITIES 



Submitted for publication Feb. 18, 1890 

By O. H. TTTTMANUNT, Assistant, 

In oharge of the Office of Standard "Weights and Measures 

Revised for republication Feb. 1, 1892 

APPENDIX NO. 6-REPORT FOR 1891 




WASHINGTON 

GOVERNMENT PRINTING OFFICE 
1892 






UNITED STATES 
COAST AND GEODETIC SUEVEY 

T. C. MENDENHALL 

SUPEKINTENDKNT 

WEIGHTS AND MEASURES 
ONTHK REDUCTION 

OF 

HYDROMETER OBSERVATIONS 

OF 

SALT WATER, DENSITIES 



Submitted for publication Feb. 18, i8go 

By O. H. TITTMANN, Assistant, 

In charge of tlie Office of Standard Weights and Measures 

Revised for republication Feb. i, 1892 



APPENDIX No. 6-REPORT FOR 1891 




WASHINGTON 

GOVERNMENT PRINTING OFFICE 
18 92 






a V 






3r 



rEB 13 1905 



APPENDIX NO. 6—1891. 



ON THE SEDUCTION OF HYDEOMETEE OBSEEVATIONS OF 
SALT-WATEE DENSITIES. 



Submitted for publication, February 18, 1890, by O. H. Tittmann, Assistant, 
in charge of tbe Office of Standard Weights and Measures. 

Eevised for republication, February 1, 1892. 



The hydrometers heretofore in use in the Coast and Geodetic Survey 
for determining the density of ocean water are described in Appendix 
16, Coast Survey Eeport for 1874. They are of glass, of the usual 
form, and are decimally divided on the stem. Each hydrometer is ac- 
companied by a copper vessel for holding the water, to which a ther- 
mometer is attached with the apparatus described in that appendix. 
Fahrenheit thermometers were used, and the densities given by the 
graduation of the hydrometer were referred to pure water at 60° F. 

The introduction of the centigrade scale and of a graduation to give 
densities referred to pure water at 4° C. necessitates the publication of 
a convenient table for reducing the observations to the temperature of 
15° C, recently adopted by this Survey and by the U. S. Fish Commis 
sion. The hydrometers hereafter issued will be standardized at this 
temperature. 

The following table for the reduction of observed densities to 15° C. 
is taken from Dittmar, Physics and Chemistry, Challenger Expedition, 
Vol. 1, after applying to his densities one-half of the correction given 
by him for reducing them to Thorpe and Bucker's results. The tem- 
perature at which the density of the standard water is 1*02600 has been 
shifted from 15 0, 56 to 15° C. for the sake of getting an integer number. 
The table has been rearranged so as to give the densities of the stand- 
ard water multiplied by 1000 for whole degrees and tenths from 0° to 
30 o, 9 C. on one page. 

The ratio designated q> (t) by Dittmar is omitted, and only its recip- 
rocal is given in the column headed m. The values there given apper- 
tain to the temperatures on the same horizontal lines given in the first 

275 



276 



U. S. COAST AND GEODETIC SURVEY. 



column. The use of 'this function is illustrated in the examples in 
which it appears as a multiplier for the purpose of allowing for the 
different rates of expansion between standard water and the water the 
density of which is being determined. 

The last column has been added to this table for convenience, and 
gives the correction for change in the volume of the hydrometer itself. 
The values given have been computed for the mean reading 1026, and 
with the assumed coefficient of cubical expansion for glass a = •000025. 

The use of the table will appear from the following examples : 



Example. 




I. 


II. 


o 

23-0 

. — 01 




10-5 

— -2 


Obs. temp. 

Corr. to thermometer. 

Corrected temp. = t. 

Observed hydr. reading. 

Corr. for expansion of hydr. — a. 

Corr. for hydrometer constant. 

Observed density at ^=OD. 
Density of standard water at /= SD. 

OD -SD. 

m, tabular multiplier. 

m(OD — SD.) 
Standard water at 15 C. 

Corrected density at 15 . 


229 
102 1 -oo 

— 0-20 


IO3 
1029-29 

+: -i2 


I020-8o 

1023-99 


1029-41 
1026-92 


— 3-19 
IOl8 


4-2-49 
•987 


— 3-25 
I026-00 


4-2-46 
1026-00 


IO2275 


1028-46 



For observations which have been reduced to 60° F., made with the 
old hydrometers indicating densities referred to pure water at 60° F., 
it will suffice to subtract the constant 0-82 from the result in order to 
convert the latter into absolute densities at 15° O. 

Example : Given 1024-00 the density of salt water at 60° F. referred 
to pure water at 60° F., 1024-00 - 0-82 = 1023-18 its density at 15° C. 



REPORT FOR 1891 PART II. 



277 



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,LSJ, RY 0F CONGRESS 

029 714 198 J 



